Modulating effect of passive immunization with anti-Mycobacterium tuberculosis antibodies on humoral response in BCG-infected mice.

Previous work has shown that the passive immunization with rabbit anti-Mycobacterium tuberculosis H37Rv antiserum of Mycobacterium bovis BCG-infected mice promotes the growth of bacilli in their spleen and induces a late production of antimycobacterial antibodies in their serum. The effect of the passive immunization on the early antibody response in infected mice has now been investigated. It was found that passive immunization with H37Rv antiserum of BCG-infected mice depressed the early humoral response as determined by the plaque-forming cell response to BCG extract when compared with BCG-infected mice treated with the antiserum freed from its mycobacterial antibodies as controls. In the BCG-infected mice treated with the rabbit antiserum freed from mycobacterial antibodies or treated with saline, the antibodies were present in the serum as soluble immune complexes which reached a peak 4 days after infection. These immune complexes were formed with mice antimycobacterial antibodies as determined with an antimouse immunoglobulin serum in the double diffusion test. On the other hand, in BCG-infected mice passively immunized with rabbit antimycobacterial serum, the immune complexes detected were mainly composed of transfer rabbit antimycobacterial antibodies as established with an antirabbit immunoglobulin serm. Comparison of the biphasic humoral response in passively-enhanced mycobacterial infection and allotransplanted normal tissue in the host is discussed.